Traffic Analysis / Modeling


Traffic analysis is used to assist traffic and geometric design of the project to optimize the layout for each alternative design. The purpose of these traffic studies is to show if there is a need for new facilities or improve existing facilities (interchanges, roads, bridges, etc.) in order to accommodate for future traffic demand in the City of Lake Elsinore.


This project includes the study and consideration of 4 alternative designs and a no-build alternative. The City of Lake Elsinore General Plan will be taken into consideration and used for all analysis done in this project. Future traffic demand will be predicted using existing data and engineering judgment. Using Trafficware Synchro Studio 8, a traffic model of the study area will be created for each alternative, including the no-build alternative. The Synchro traffic model will assist in determining whether geometric layout can accommodate for the traffic demand, if not, the traffic team will work with the geometrics team to adjust the geometric layout. This iterative process will determine the best geometric layout with the best traffic results for the alternative design. A level of service (LOS) grade will be given for each intersection according to the HCM 2000 standards to better analyze the ability of the proposed alternatives to account for future traffic demands. Traffic delays are also calculated and considered using Sim Traffic software to assess the amount of time lost at each intersection. Intersection Control Evaluation (ICE) is performed for each intersection to optimize the intersection control type. For freeway analysis, basic freeway segments calculations, merge/diverge influence area calculations, and weaving segments calculations are performed to further analyze our study area.

Tight Diamond Interchange

The Tight Diamond Interchange is a simple and common interchange design. The tight diamond is the current design of the Railroad Canyon Road interchange and the Main Street interchange. It is most effective where there are physical, geometrical, or right-of-way restrictions and. It is also beneficial for drivers to have similar interchange designs at consecutive interchanges. Diamond interchanges usually have minimum construction costs. However, the tight diamond design creates a short distance between ramp intersections at the local street and it does not allow for future improvements or expansions to the interchange.

The Synchro traffic model, delays and levels of services (LOS) of intersections, and simulation video are shown below. Intersection controls were determined using Intersection Control Evaluation (ICE). Delays were calculated using Sim Traffic, and the LOS values were based on HCM 2000. Roundabout LOS is based on HCM 2010 roundabout analysis.

spui_map tdi_chart

Below is the video modeling for this alternative.

Split Diamond Interchange

The Split Diamond Interchange utilizes frontage roads that connect the new Franklin interchange to the existing Main Street interchange. The northbound off-ramp and southbound on-ramp are located at New Franklin St., while the southbound off-ramp and northbound on-ramp are located at Main St. The frontage roads provide quick access between interchanges for drivers using the I-15 and direct some traffic away from local streets.

The Syncho traffic model, expected delays, level of service, and simulation video for the Split Diamond Interchange are shown below. All intersection control types were determined using ICE (Intersection Control Evaluation). Delays were calculated from the SimTraffic, and levels of service were obtained using HCM 2000 standards.

sdi_map sdi_chart

Below is the video modeling for this alternative.

Partial Clover Interchange

The Partial Clover Interchange consists of 4 on and off-ramps all located on the south side of the new Franklin Street bridge. This increases the distance between the ramps at Main St and the ramps at New Franklin Street The partial clover interchange alternative also increases the distance between the ramp intersections at the local street, which in turn increases the capacity between intersections on the local street. This alternative also allows pedestrians and bicyclists to travel along the westbound sidewalk of the new bridge with little to no conflicts.

The Synchro traffic model, expected delay and level of service, and simulation video for the Partial Clover Interchange are shown below. Intersection controls were determined by the use of ICE (Intersection Control Evaluation). Delays were obtained from SimTraffic and the levels of service were obtained using HCM 2000 standards. Roundabout levels of service were based on HCM 2010 roundabout analysis.

cfi_map clover_chart

Below is the video modeling for this alternative.

Single Point Urban Interchange

The Single Point Urban Interchange (SPUI) geometrically appears similar to a Diamond Interchange. However, unlike the Diamond Interchange that utilizes two ramp intersections, the SPUI converges all through and turning movements into a single intersection. This allows the interchange to efficiently accommodate large traffic volumes in a limited space. A couple of drawbacks are that the SPUI is expensive to construct, and drivers do not expect this type of intersection due to its limited use in Southern California.

The Synchro traffic model, expected delay and level of service, and simulation video for the Single Point Urban Interchange (SPUI) are shown below. Control types for the intersections shown were selected using Intersection Control Evaluations (ICE). Delays were determined using 1 hour simulation intervals for SimTraffic. The levels of service were obtained using HCM 2000 standards for signalized intersections and HCM 2010 Roundabout analysis for roundabout control.

ddi_map spui_chart

Below is the video modeling for this alternative.

Projected / Future Volumes

The No Build intersection turning movements and ramp volumes were provided by Caltrans. Turning movements were adjusted to accommodate the proposed bridge and interchange. Traffic teams from Railroad and Franklin collaborated with each other to determine which turning movements are increased or decreased with the construction of a new interchange at Franklin St. Turning movements were adjusted by allocating most of the turning volume to the shortest travelled path to their destination. For intersections where the turning movements are unknown, the unknown turning movements were adjusted to behave like a similar intersection nearby. The City of Lake Elsinore's General Plan was used to determine proposed residential and commercial zoning of the study area. This information was also used to predict turning movements and volumes.

Basic Freeway Segments

Basic freeway segments are located outside of merge, diverge, and weaving influence areas. Traffic flow within these basic segments vary depending on several factors such as volumes, speed, grade, interchange spacing, freeway geometry, etc. Density, measured in vehicles per hour, is calculated using these factors. The calculated density is used to determine the performance of traffic flow, or level of service (LOS). The LOS for the I-15 was calculated for the basic freeway segments beginning from the adjacent interchanges to Franklin St. The LOS was determined for 3 independent cases, (1) the existing (2009 year) volumes/geometry, (2) the project (2040 year) volumes and existing geometry, and (3) the project (2040 year) volumes and ultimate build out of the freeway.

Merging / Diverging Influence Areas

Using the Highway Capacity Manual 2010 (HCM 2010), we performed merge and diverge calculations. Merge and diverge areas are located on the mainline at the on- and off-ramps of a local street interchange. The merge influence area at an on-ramp includes the acceleration lane(s) and the 2 lanes immediately adjacent to the acceleration lane for a distance of 1,500 ft downstream from the merge point (where the acceleration lane(s) and mainline lanes starts to become parallel). The diverge influence area at an off-ramp includes the deceleration lane(s) and the 2 lanes immediately adjacent to the deceleration lane for a distance of 1,500 ft upstream from the diverge point (where the deceleration lane(s) and mainline lanes cease to be parallel).

The purpose of merge and diverge analysis is to provide a level of service (LOS) of the merge or diverge influence area. The LOS is calculated based on the density of the influence area. The density is calculated using a methodology provided by the HCM 2010 that includes influential factors such as volumes of ramps and freeway segments, acceleration and deceleration lengths, upstream and downstream ramp distances, etc. This analysis was performed for the case of 2040 Franklin Street interchange alternative with 2040 Railroad Canyon Road no-build.